1. Field of the Invention
The present invention relates generally to systems and methods applicable to chromatography and electrophoresis, and more particularly to a system and method for chromatography and electrophoresis using circular optical scanning.
2. Discussion of Background Art
Chromatography is a technique for separating molecules based on how they tend to cling to or dissolve in various solids, liquids and gases. Electrophoresis is also a technique for separating large molecules (such as DNA fragments or proteins) from a mixture of similar molecules. However, in electrophoresis, an electric current is passed through a medium containing the molecules. Each type of molecule travels through the medium at a different rate, depending on its electrical charge and size, which creates a series of identifying bands.
Many chromatography and electrophoresis systems, having multiple analysis columns within a microchannel plate, use scanning optical detection systems based on Laser Induced Fluorescence (LIF) or UV absorbence to detect the presence of analytes as they travel past the scan path of an optical detection beam. These scanning detection systems typically include a high intensity light source (e.g. laser), one or more optical detectors (e.g. Photo-Multiplier Tubes (PMTs) or Charge Coupled Devices (CCDs), various electronic circuits (e.g. amplifiers, filters, A-to-D converters), and a computer for control, data collection, and storage.
FIG. 1 is a block diagram of a prior art 100 system using "linear" optical scanning. The prior art optical scanning systems 100 use linear scan motors to move the light source back and forth in a straight line 102 across the analysis columns in the microchannel plate so as to periodically excite and detect the presence of analyte molecules. The number of analysis columns that can be detected in these linear scanned systems is limited principally by the width of the array of columns, the velocity of the analytes as they move past the detecting light beam, the intensity of the illuminating light beam on the analyte, and the spatial resolution, accuracy, and maximum speed with which the linear scan stage can be driven (usually via an electric motor). High resolution, accuracy and low vibration requirements limit current stepper motors and servo motors limit the maximum velocities of linear scan stages to approximately 30 cm/sec and therefore, limit the number of analysis columns that can be detected to approximately 100 analysis columns maximum. This is because for wider microchannel plates, some of the analyte molecules on one end of the microchannel plate may pass through the linear detection area before the linear detector can return to the analysis columns in which they are contained.
Recently, efforts are being made to sequence all the molecules in the human genome as soon as possible. Due to this and other growing needs for even faster chromatography and electrophoresis systems, linear systems limited to only 100 analysis columns are too constricting.
In response to the concerns discussed above, what is needed is a system and method for chromatography and electrophoresis that overcomes the problems of the prior art.